Vibration And Noise Analysis And Optimization Of Two-Speed Gearbox Of Pure Electric Vehicle

With people’s increasing attention to environmental problems,electric vehicles become a fashionable transportation because their characters as energy saving,environmentally friendly and efficient electric.As the main component of electric vehicle transmission system,its vibration and noise level will have a huge impact on the NVH performance of the whole vehicle.Therefore,it is necessary to analyze the dynamic response of the gearbox and optimize design of the gear system,so as to further improve the transmission performance of the whole vehicle.In this thesis,with the aim of reducing the vibration and noise of a pure electric vehicle gearbox,dynamic response analysis and gear optimization design have carried out.The main research contents are as follows:To begin with,considering the vibration and noise caused by dynamic excitation of transmission gear system,a dynamic model of planetary gear system was established.The dynamic response of sun gear,planet gear and planet carrier under internal and external dynamic excitation was calculated,and the dynamic response characteristics of planetary gear system were obtained by time domain analysis,frequency domain analysis and spectrum analysis.Furthermore,the influence of internal dynamic excitation on the dynamic response of planetary gear transmission system was analyzed by changing the error amplitude of gear teeth.Moreover,considering the influence of the deformation of the flexible parts of the transmission,the rigid-flexible coupling analysis model of the transmission was established.The safety and reliability of various parts of the transmission under multiple working conditions are analyzed.Considering the influence of the transmission error of gear,the transmission error and contact spot of meshing gear pair were obtained by analyzing the microscopic geometry of gearbox.On this basis,a concept of boundary load ratio has proposed to describe the contact condition of gear,and the sensitivity analysis of gear modification parameters has carried out to determine the influence of different gear modification parameters on the transmission error and contact spots.Subsequently,the modification parameters of the gearbox gear were optimized to reduce the vibration noise of the gearbox.Based on the analysis results of gear modification parameters,a forward search method has proposed to determine the basic range of gear modification parameters.The equations of peak-to-peak transmission error,boundary load ratio,contact tooth surface load coefficient and gear modification parameters were established by polynomial response surface proxy model.Nondominated sorting genetic algorithm-II(NSGA-II)was used to optimize the micro-gear modification parameters,and the optimal gear modification parameters were determined by combining combination ordered weighted averaging(C-OWA)and technique for order preference by similarity to an ideal solution(TOPSIS).Finally,the vibration response and acoustic response of the gearbox before and after the optimization were analyzed under different load conditions,and the correctness of the vibration response results was verified by the gearbox test bench.The results show that the vibration response and acoustic response of the gearbox under different load conditions are decreased after the optimization of the gear.The vibration and noise reduction of the gearbox is realized,the NVH performance of the gearbox is improved.